AlGaAs structures with different aluminum concentration (xϭ0.0, 0.17, 0.30, and 0.40͒ were characterized by photoluminescence and photoreflectance techniques. The temperature dependence of optical transitions in the temperature ranging from 2 to 300 K were investigated.

Photoluminescence ͑PL͒ spectroscopy and atomic-force microscopy ͑AFM͒ were used to investigate the size evolution of InAs quantum dots on GaAs͑001͒ as a function of the amount of InAs material. Different families of islands were observed in the AFM images and unambiguously identified in the PL spectra, together with the signal of the wetting layer. PL measurements carried out at low and intermediate temperatures showed a thermal carrier redistribution among dots belonging to different families. The physical origin of this behavior is explained in terms of the different temperature dependence of the carrier-capture rate into the quantum dots. At high temperatures, an enhancement of the total PL-integrated intensity of the largest-sized quantum dots was attributed to the increase of diffusivity of the photogenerated carriers inside the wetting layer.

The zone-center optical phonons of layer materials GaSe, GaTe, and their solid solutions are studied by means of Raman scattering. Most of the structure in the hitherto unstudied spectrum of GaTe is identified by following their evolution in the solid solutions and relating them to already known bands in GaSe. Increased layer-layer interaction, as solutions become richer in Te, allow the observation of Davydov splittings. Detailed study of the spectra of GaSe, "Te"reveal an abrupt phase transition from hexagonal to monoclinic structures in the composition range 0.26 & x & 0.60. Both oneand two-mode behaviors are observed in the phonon bands of the solid solutions.

No abstract

Articles you may be interested inEffect of quantum confinement on shallow acceptor transitions in δ-doped GaAs/AlAs multiple-quantum wells Appl. Phys. Lett. 84, 735 (2004); 10.1063/1.1644912Effect of quantum-well confinement on acceptor state lifetime in δ-doped GaAs/AlAs multiple quantum wells Appl.